It's not like making an MMORPG out of Zelda, or any game for that matter, "destroys" it. A side-project, spin off, or whatever is rad enough, people who want to play it will and people who don't won't, and it's as simple as that.
Metroid? Why WOULDN'T metroid have an online death match? If the Revolution release doesn't it'll be one of Nintendo's biggest mistakes ever. Just look at Halo and Halo2 on xBox's live's popularity.
PS: Ian Sane; do you post on the Operationivy.com forums??